<p>Biogeography of introgression across Nigeria.</p>

<p><b>(A)</b> A supervised Admixture analysis was used to estimate <i>S. haematobium</i> (green), <i>S. bovis</i> (orange), and <i>S. curassoni</i> (blue) ancestry in each parasite. Known hybrids—including an F1 <i>S. haematobium × S. bovis</i> hybrid [<a href="plospathogens.org/article/info:doi/10.1371/journal.ppat.1014625#ppat.1014625.ref067" target="_blank">67</a>] and both F1 and early backcross natural <i>S. curassoni × S. bovis</i> hybrids [<a href="plospathogens.org/article/info:doi/10.1371/journal.ppat.1014625#ppat.1014625.ref019" target="_blank">19</a>]—show high levels of mixed ancestry from their parental species.

In contrast, we found no evidence of high levels of mixed ancestry in miracidia collected from humans. Instead, nearly all parasites collected in southern Nigeria carry low levels of livestock parasite ancestry, never exceeding 18.4% (mean 4.9%). “Africa” refers to published sequences from collection localities in Angola, Corsica, Cote d’ Ivoire, Madagascan, Namibia, Sao Tome, Senegal, Swaziland, Tanzania (Zanzibar), Uganda, and Zambia. <b>(B)</b> Mean <i>S. haematobium</i> ancestry values across sampling locations in Nigeria are shown on the map.